cgitsb/README


                       cgit - cgi for git


This is an attempt to create a fast web interface for the git scm, using a 
frontside cache to decrease server io-pressure.

When cgit is invoked, it looks for a cached page matching the request. If no
such cachefile exist (or it has expired), it is (re)generated. Finally, the
cachefile is returned to the client.

If the cachefile has expired, but cgit is unable to lock the cachefile, the 
client will get the stale cachefile after all. This is done to favour page
throughput over page freshness.

Also, when a cachefile is generated, a few cache-related http-headers are
created: "Modified" is set to current time(2), while "Expires" is set to 
time(2) + <cachefile TTL> * 60 (unless the TTL is negative, in which case it
is read as "60 * 60 * 24 * 365"). This is done to avoid repeated requests for
already visited pages.

The following cache-related options can be set in /etc/cgitrc:

  cache-root=<path>           root directory for cache files
  cache-root-ttl=<min>        TTL for the repo listing page
  cache-repo-ttl=<min>        TTL for repo summary pages
  cache-dynamic-ttl=<min>     TTL for pages with symbolic references
  cache-static-ttl=<min>      TTL for pages with sha1 references

The cachefiles are split into different directories, based on the requested
repository and page:

  Repo listing:  <cachedir>/index.html
  Repo summary:  <cachedir>/<repo>/index.html
  Repo subpage:  <cachedir>/<repo>/<page>/<querystring>.html
Add caching infrastructure This enables internal caching of page output. Page requests are split into four groups: 1) repo listing (front page) 2) repo summary 3) repo pages w/symbolic references in query string 4) repo pages w/constant sha1's in query string Each group has a TTL specified in minutes. When a page is requested, a cached filename is stat(2)'ed and st_mtime is compared to time(2). If TTL has expired (or the file didn't exist), the cached file is regenerated. When generating a cached file, locking is used to avoid parallell processing of the request. If multiple processes tries to aquire the same lock, the ones who fail to get the lock serves the (expired) cached file. If the cached file don't exist, the process instead calls sched_yield(2) before restarting the request processing. Signed-off-by: Lars Hjemli <hjemli@gmail.com> 2006-12-10 22:31:36 +01:00
Remove implementation details from README Let README describe the "bigger picture" instead. Signed-off-by: Lars Hjemli <hjemli@gmail.com> 2006-12-13 02:06:29 +01:00			`cgit - cgi for git`


			`This is an attempt to create a fast web interface for the git scm, using a`
			`frontside cache to decrease server io-pressure.`

			`When cgit is invoked, it looks for a cached page matching the request. If no`
			`such cachefile exist (or it has expired), it is (re)generated. Finally, the`
			`cachefile is returned to the client.`

			`If the cachefile has expired, but cgit is unable to lock the cachefile, the`
			`client will get the stale cachefile after all. This is done to favour page`
			`throughput over page freshness.`

			`Also, when a cachefile is generated, a few cache-related http-headers are`
			`created: "Modified" is set to current time(2), while "Expires" is set to`
			`time(2) + <cachefile TTL> * 60 (unless the TTL is negative, in which case it`
			`is read as "60 * 60 * 24 * 365"). This is done to avoid repeated requests for`
			`already visited pages.`

			`The following cache-related options can be set in /etc/cgitrc:`

			`cache-root=<path> root directory for cache files`
			`cache-root-ttl=<min> TTL for the repo listing page`
			`cache-repo-ttl=<min> TTL for repo summary pages`
			`cache-dynamic-ttl=<min> TTL for pages with symbolic references`
			`cache-static-ttl=<min> TTL for pages with sha1 references`

			`The cachefiles are split into different directories, based on the requested`
			`repository and page:`

			`Repo listing: <cachedir>/index.html`
			`Repo summary: <cachedir>/<repo>/index.html`
			`Repo subpage: <cachedir>/<repo>/<page>/<querystring>.html`